It looks like Enterprise Library 5 will use the default database of whatever web.config is loaded first. E.g. if /Aba/Test.aspx is loaded first then the default database will be set to the value in /Aba/web.config. You are correct -- this changed
sometime between version 2 and version 5. I haven't looked in depth but I would guess it has to do with how Unity creates and loads the build plans for the various database objects.

The way to get the database that you want is to go after it directly by name. E.g. DatabaseFactory.CreateDatabase("frusanaba"). This should work fine. However, I take it you still want to rely on configuration to determine the database
instead of hard coding the database key in the code. So you could create your own defaultDatabase appSettings value and then use that via a helper method.